1. Field of the Invention
The present invention relates to a flat panel display, and more particularly, to an organic electroluminescent display in which a pixel electrode and a black matrix with a concentration gradient of a transparent material and a metallic material are formed on the same surface of a substrate, and a method of fabricating thereof without an additional masking operation.
2. Description of the Related Art
FIG. 1 illustrates a cross-sectional view of a conventional active matrix organic electroluminescent display.
Referring to FIG. 1, a thin film transistor (TFT) and a capacitor are formed on a first region 101 of a dielectric substrate 100, on an upper part of which a buffer layer 110 is formed. The thin film transistor is equipped with source/drain regions 125 and 126 which are formed on a semiconductor layer 120, a gate electrode 131 which is formed on a gate insulating layer 130, and source/drain electrodes 151 and 152 which are formed on an interlayer insulating layer 140 so as to be electrically connected to the source/drain regions 125 and 126, respectively, through contact holes 141 and 142.
The capacitor is equipped with a first electrode 135 formed on the gate insulating layer 130 and a second electrode 155 connected to the source electrode 151. A part interposed between the first and second electrodes 135 and 155 in the interlayer insulating layer 140 functions as a dielectric layer of the capacitor.
An organic electroluminescent display device is formed on the second region 102 of the dielectric substrate 100. The organic electroluminescent display device is equipped with a pixel electrode 170 which is formed on a passivation layer 160 so as to be electrically connected to the drain electrode 152 through a via hole 161, an organic electroluminescent layer 190 which is formed on the pixel electrode 170 exposed through an opening part 185, and a metal electrode 195 which is formed on a planarization layer 180 comprising the organic electroluminescent layer 190.
A flat panel display such as an active matrix organic light emitting device (AMOLED) with the foregoing structure includes a switching device and various wirings to impress power supply to the switching device, wherein an external light is reflected by a metallic material of the wirings.
For example, contrast is greatly deteriorated since the external light is reflected by a metallic material which is used to form a gate electrode and a lower electrode of the capacitor, an electrode material which is used to form source/drain electrodes and an upper electrode of the capacitor, and an electrode material which is used to form a cathode.
To prevent the deterioration of contrast due to a reflection of external light, an expensive polarizer has been adhered to a front surface of a conventional organic electroluminescent display. However, in addition to an increase in manufacturing cost due to the use of the polarizer, transmittancy of the display is deteriorated. That is, since the polarizer itself blocks light emitted from an organic electroluminescent layer of the display, luminance is also decreased.
Furthermore, in a conventional display, a black matrix comprising Cr/CrOx or an organic layer is separately formed on a region where a thin film transistor and a capacitor are formed. However, a conventional fabrication method thereof is complex and problematic as the method necessarily requires a separate masking operation to form the black matrix.